Aqueous separator slurry composition

Abstract

The invention relates to an aqueous slurry composition comprising an aqueous-based polymeric binder and anionic oxide nanoparticles that can be used, for example, in coating of electrodes and/or separators in electrochemical devices. This coating after drying, is highly porous, electronically isolating, and exhibits high dimensional stability at elevated temperatures.

1 . An aqueous slurry composition comprising:
 a) at least one polymeric binder, and   b) at least one anionic oxide nanoparticle having a volume average particle size of between 5nm to 500 nm; and   
       wherein the zeta potential of the aqueous slurry composition is negative. 
     
     
         2 . The aqueous slurry composition of  claim 1 , wherein the anionic oxide nanoparticle comprises at least one of zinc oxide, aluminum oxide, zirconia, or silica. 
     
     
         3 . The aqueous slurry composition of  claim 1 , wherein the anionic oxide nanoparticle comprises anionic fumed aluminum oxide and has a volume average particle size of between 5nm and 200 nm. 
     
     
         4 . The aqueous slurry composition of  claim 1 , wherein the anionic oxide nanoparticles have a surface area of from 15 to 600 m 2 /g. 
     
     
         5 . The aqueous slurry composition of  claim 1 , wherein the weight ratio of anionic oxide nanoparticles to polymeric binder is between 5:95 and 95:5. 
     
     
         6 . The aqueous slurry composition of  claim 1 , wherein the weight ratio of anionic oxide nanoparticles to polymeric binder is between 15:85 and 85:15. 
     
     
         7 . The aqueous slurry composition of  claim 1 , wherein the solids content of the aqueous slurry is from 10% to 70 wt % based on total weight of the aqueous slurry composition. 
     
     
         8 . (canceled) 
     
     
         9 . The aqueous slurry composition of  claim 1 , wherein the zeta potential of the aqueous slurry composition is negative zeta potential less than negative 10 mV. 
     
     
         10 . The aqueous slurry composition of  claim 1 , wherein the viscosity is less than 20,000 cP. 
     
     
         11 . The aqueous slurry composition of  claim 1 , wherein the polymeric binder comprises both a water soluble polymeric binder and a water insoluble polymeric binder. 
     
     
         12 . The aqueous slurry composition of  claim 1 , wherein the polymeric binder comprises at least one of SBR, acrylic binders, PVDF binders, or mixture thereof. 
     
     
         13 . The aqueous slurry composition of  claim 1 , wherein the polymeric binder comprises at least one water soluble binder selected from the group consisting of PAA, CMC, PVA, HASE, and ASE, or mixtures thereof. 
     
     
         14 . The aqueous slurry composition of  claim 1 , wherein the anionic oxide nanoparticles have a fractal shape. 
     
     
         15 . The aqueous slurry composition of  claim 1 , further comprising inorganic particle having a particle size of 1 micron or greater. 
     
     
         16 . A separator for a secondary battery comprising a coating composition, said coating composition comprising a) at least one polymeric binder and b) at least one anionic oxide nanoparticle having a volume average particle size of between 5nm to 500 nm. 
     
     
         17 . (canceled) 
     
     
         18 . A separator for a secondary battery comprising the composition of  claim 1  in dried form. 
     
     
         19 . (canceled) 
     
     
         20 . A method of making a separator for a battery comprising 1) providing an aqueous slurry composition comprising a) at least 5 weight percent anionic oxide nanoparticles and b) at most 95 wt % polymeric binder, wt % based on total weight of the anionic oxide nanoparticle and polymeric binder, and c) optionally inorganic particles having a particle size of 1 micron or greater, 2) applying the aqueous slurry composition on a substrate, 3) drying the aqueous slurry to form the coating on the substrate. 
     
     
         21 . The method of  claim 20 , wherein the substrate is an electrode. 
     
     
         22 . The method of  claim 20 , wherein the substrate is a free standing separator. 
     
     
         23 . The method of  claim 20 , wherein the aqueous slurry is applied simultaneous with an electrode slurry in a wet on wet method. 
     
     
         24 . The method of  claim 20 , wherein the aqueous slurry is the slurry of  claim 1 .